RENEWABLE ENERGY
An ESS Energy Warehouse is moved via crane
Te founders of ESS recognised the potential of iron flow technology to provide lower-cost LDES compared with competing technologies. Te R&D team realised that the fundamentals of iron flow stability lie in understanding how the equilibrium potential of electrochemical reactions changes against pH. During charge of the iron flow battery,
the reaction at the negative electrode that forms iron metal competes with a reaction that will form hydrogen. Tis sees protons in the electrolyte accepting electrons to form hydrogen gas, H2. In addition, the plated iron metal may corrode in an acidic electrolyte to produce ferrous ion, Fe2+ also generate H2
.
Tese side reactions cause electrolyte charge imbalance and pH imbalance as the electrolyte becomes increasingly comprised of Fe3+
of hydrogen gas leads to an increasingly alkaline solution. Te excess Fe3+
combine with the OH ions and form Fe(OH)3
and the loss of protons in the form ions
, which forms a precipitate. Over
a series of cycles, these reactions reduce the battery’s performance. Researchers at ESS developed the
company’s proprietary Electrolyte Health Management System (EHMS) to manage these side reactions, enabling iron flow
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ESS technology is supporting the energy transition across the world
batteries to deliver unlimited cycling without degradation. A key component of the EHMS is the “proton pump”, which manages pH balance of the electrolytes, ensuring consistent performance over thousands of cycles.
Te EHMS stabilises the battery by reacting the unbalanced Fe3+
ions from , and
the positive electrolyte with the hydrogen gas by-product from the negative side. Tis is achieved by converting hydrogen gas back into protons and pumping them into the positive electrolyte. Tis proton pump has the effect of stabilising the pH across the battery and ensuring that the positive electrolyte returns fully reloaded with Fe3+
of charge of the negative electrode. Te EHMS is a closed-loop system, and the proton pump is inherently self-limiting, reducing OPEX costs and enabling unlimited cycling over the battery’s 25-year design life.
IRON-FLOW BATTERIES IN ACTION
ions to match the state
LDES technologies that complement intermittent renewable energy sources can enable renewable energy to be baseload energy. ESS’ iron-flow battery technology can deliver 6-12 hours of flexible energy storage capacity with a cost-effective, safe and nontoxic alternative to competing LDES technologies. ESS technology is already being deployed to support the global energy transition; the company most recently signed an agreement with Sacramento Municipal Utility District (SMUD), one of the largest municipal utilities in the USA, which includes 200MW/2GWh of LDES to support SMUD’s ambitious 2030 Clean Energy Vision.
Alan Greenshields is European Director at ESS.
www.essinc.com
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